Air nozzle for flat-spraying appliances



Aug. 4, 1936. E. GUSTAFSSON 2,049,700

' AIR NOZZLE FOR FLAT SPRAYING APPLIANCES Filed July 15, 1955 2Sheets-Sheet l Ill] ill/Ill]!!! Eric 6 66 1100 E. GUSTAFSSON AIR NOZZLEFOR FLAT SPRAYING APPLIANCES Aug. 4, 1936.

Filed July 15, 1955 2 Sheets-Sheet 2 Inventor. lfkic C f fww PatentedAug. 4, 1936 NE'E'ED STATES AIR NOZZLE FOR FLAT-SPRAYING v APPLIANCESEric Gustafsson, Chicago, Ill., assignor to Binks ManufacturingCompany,-Chicago, 111., a corporation of Delaware Application July 15,1935, Serial No. 31,350

12 Claims.

My invention relates to spray appliances constructed for having aforwardly projected (and usually partially aerated) stream of materialflattened by the impact of two opposed jets of air to a substantiallyelliptical or elongated rectangular section and thereafter spread outinto a fan-shaped spray. Modern spray guns of this class usually providea separate air control for the side air jets, whereby the cross-sectionof 1') the resulting spray (which would be circular without such sidejets, and elliptical with a relatively light impact of these side jets)can be adjusted to afford the commercially most desirable pattern-namelyone having substantially parallel longitudinal sides of much greaterlength than their spacing, and having only slightly rounded orsubstantially straight ends.

In one of its major objects, my invention aims to provide simple meansfor reducing the offspray beyond the general pattern of the spray,

and particularly that beyond the ends of the pattern, "so as to permit aclean-contoured pattern to be produced even at a high spraying rate,without requiring an undesirably large total consumptionof compressedair. Moreover, my invention aims to provide means for this purpose whichcan readily be varied according to the nature of the projected material,and also to suit other operating conditions, and which means can readilyconsist of simple auxiliary bores pro- 1 vided in the usual air nozzleof a modern spray gun.

When a non-homogeneous material, as for example vitreous enamel(consisting of finely ground vitreous material suspended in a carriedliquid) is flat-sprayed from a conventional modern spray gun and thematerial stream is sulficiently flattened to produce such aparallelsided pattern, the resulting spray is apt to project anundesirable amount of so-called off-spray beyond the general contour ofthe pattern, and particularly beyond the ends of the elongated pattern,thereby marring the desired uniformity of the coating.

The just recited difficulty was overcome, as disclosed in United StatesPatent #1397173 (issued February 3, 1933 to Robert Long and myself) byprojecting additional air against the two sides of the material streamtoward which the spray is to be spread, so as to preflatten this stream,be-

fore it receives the impact of the side air jets, to

an elliptical section having its longer axis in the same plane with theaxes of the side air jets.

This proved quite satisfactory in practice, both for reducing theso-called ""off-sp-ray' with vitreous enamels andalso for producing acleaner-edged pattern with'many other coating materials, when thesematerials were sprayed at a rate which formerly was considered asadequately fast.

However, in more recent years many large users 5 of spray guns-such asthe automobile manufacturershave desired a considerable reduction in thespraying time, namely the time required for spray-coating a givensurface area, and when used at such speedier spraying rates, spray gunsl0 equipped with the air nozzle of the aforesaid patent have required anundesirably large total consumption of compressed air.

This I judge to be due to the following reasons:

To reduce the spraying time, the material must 15 be projected at higherspeed, as also the air which issues from the air nozzle around and inmerging relation to the projected material stream. In addition, theaugmented air 'forpre-flattening the stream according to the aforesaidpatent 20 must issue at a correspondingly greater rate, particularlysince considerable energy is required for forcibly deforming such amaterial stream to a changed cross-section. Moreover, more air isrequired from the side air jets for their flatten- 25 ing action thanwould have been needed if the stream hadnot been preflattened in adirection transverse to that in which the spray is to be flattened. Inaddition, the preflattening action somewhat reduces the speed of thematerial 30 stream, thereby requiring additional air to be used forpropelling it at the desired rate.

In considering the problem of avoiding a fraying of the side edges ofthe fan-like shape of the flattened stream part which later on spreads35 farther into a spray, and in which such fraying produces off-spray atthe ends'of the spray pattern, with a view to devising an air-savingsub-v stitute for the Long and Gustafsson air nozzle,

I have made these observations: 40

(a) This fan-likestream part presents rearwardly and laterally convexedshoulders at opposite sides of the axis of the stream, into whichshoulders the initially terete (or slightly flaring) cylindrical streamscurvedly merge; In each 45 shoulder portion adjacent to the curvingmerging, the stream usually spreads (laterally of the fan shape) atleast as fast as it moves forwardly, which implies that the lateralvelocity of the stream particles in such a portion of the stream 50,

effective in deterring the fan-edge, fraying which later on produceoff-spray at the ends of the elongated spray pattern.

(1)) These shoulder portions are much thinner than the diameter of theinitially projected stream, so that air jets projected against suchportions should be far more efficient in preventing a fan-edge frayingthan when projected against the unflattened stream portion after themanner of the aforesaid patent.

(c) When forwardly converging air jets are projected (for the herediscussed purpose) against such shoulder portions of the fan-shapedstream part with the jet axes in the plane along which the stream wasflattened, each such jet (when of suitable size) will straddle the edgeof such a shoulder portion so as to smooth both the fan-edge contour ofthe shoulder and considerable portions adjacent to that edge, therebyalso producing a generally sharper and cleaner edge in the spraypattern.

(d) That auxiliary air jets can effectively be directed against the saidshoulders for my above recited purposes at considerably varying angles,thereby varying the extent to which these jets aid in propelling thematerial stream and also permitting such auxiliary air jets to be usedef ficiently with materials of widely varying characteristics.

Illustrative of the manner in which I have utilized my above recitedobservations by adding suitably positioned auxiliary air ports to aconventional type of an air nozzle for a spray gun,

Fig. 1 is a front elevation of an air nozzle having two auxiliary airports in the novel disposition of my present invention, with the axes ofthese ports converging at an angle of 60 degrees.

Fig. 2 is a diametric cross-section taken in the plane along which thespray is to be flattened (namely, along the line 2-2 of Fig. 1) throughthe same air nozzle and through a material nozzle associated with it,including contours of the material stream, the central port air whichmerges with this stream, and the side air jets.

Fig. 3 is a diametric cross-section through the same two nozzles, takenin a plane at right angles to that of Fig. 2, showing the air jetsemitted from the auxiliary air ports and their effect on the fan-shapedspreading of the material by the side air jets.

Fig. 4 is a cross-section of the resulting spray, taken along the line4-4 of Fig. 3, with dotted portions showing the increased length whichthis section would have had if my auxiliary air ports had been omitted.

Fig. 5 is a reduced elevation of the more rectangular, orparallel-sided, spray pattern which would be produced if more side airwere projected than for the elliptical pattern of Fig. 4.

Fig. 6 is a front elevation of an air nozzle allied to Fig. l, but alsoincluding supplemental ports-arranged after the manner of my UnitedStates Patent #l,990,824 for producing ribs on the material stream,against which ribs the side air jets impact.

Fig. 7 is a section, taken along the line 11 of Fig. 6 through the airnozzle of that figure and the material nozzle associated with it,showing the action of this nozzle assembly.

Fig. 8 is a'front elevation of an air nozzle in which my auxiliary airports are positioned for projecting air jets with their axes convergingat an angle of 40 degrees.

Fig. 9 is an enlarged section taken along the line 9-9 of Fig. 8, withcontour lines indicatin the resulting. action.

Fig. l l is an enlarged section, taken along the.

auxiliary jet axis a of Fig. 3 and at right angles to the plane of thedrawing, showing how the air jet projected along that axis straddles theshoulder portion of the material stream against which that jet isdirected.

In the drawings, Fig. 2 shows a conventional material nozzle I having acylindrical-tubular tip T for projecting an initially circular sectionedmaterial stream. Fitted upon this material nozzle in a long customarymanner is an air nozzle N having a central air port C coaxial with andfreely housing the material nozzle tip, so as to permit air 5 to issuefrom that port around and in merging relation to the material stream Sas shown diagrammatically in Fig. 2. In addition, the air nozzle has theusual side air ports P for projecting side air jets J against oppositesides of the material stream to flatten the latter.

If the air nozzle had only the just recited tea-- tures, the projectingof the side air jets with their axes intersecting at a point X on thestream axis 2 would flatten the forwardly projected material streamapproximately as shown in Fig. 2, and with a given pressure of the sideair would give the unitary flattened part of the stream (before thisbreaks up) a fan-shaped contour f such as is shown in dotted lines inFig. 3, with the base end of the fan shape merging by curves 3 intolaterally opposite shoulder portions 4, each of which is convexed bothrearwardly and laterally away from the axis of the material stream.

To form such contour shoulders, part of the material, while movingforwardly for a distance d (Fig. 3) just beyond the ourvedly flaredstream portion 3 must move quite rapidly away from the stream axis.Consequently, the momentum imparted by this velocity to any relativelyheavy particles of the material will tend to project such particlesfarther (laterally away from the stream axis) than the lighter materialconstituents.

In practice, both the viscosity of the lighter portions of the material(as for example, the liquid in which vitreous granules are suspended)and the surface tension of the liquid tend to deter the heavierparticles from being flicked out of the lighter material'portionsimmediately. But the greater weight of the heavier particles apparentlybegin to separate minute streamer-like liquidcoated portions of thematerial stream before the material has moved forwardly far beyond theshoulder portions reaching through the said distance d, and some of theflicking tendency apparently begins even in the stream portion (behindthe said shoulders) which has the curved edges 3. a

To prevent the deleterious eifect which the just recited actions have onthe spray pattern, I provide two auxiliary air ports each disposed forprojecting an auxiliary air jet against one of the said shoulders so asto act on the fan-edge portions of the material stream in which theabove described lateral movement of the stream par ticles is relativelyrapid. These auxiliary port's .A have. their axes a symmetricallydisp'osed'with respect to the axis 2 of the central airport, and in theplane 6 (diametric of the said central port) along with the spray isflattened, namely a *plane at right angles to the common plane of theaxes p of the side port P.

Moreover, each .auxiliary port is positioned so that the air jet 9'projected by it will .be freely spaced from the unflatt'ened part of thematerial stream, and each such port preferably has its bore diameter aminor fraction of that of the 7 central air port 0. In addition, eachauxiliary port A preferably is disposed for projecting its air eitherentirely against an edge portion of the fan contour of the flattenedstream part, which portion is adjacent to the juncture :of one of thesaid convexed shoulders with the curved merging of the shoulder into thenot yet flattened part of the stream,

' Working within the above recited limits, which prolonged experimentshave shown -to'be desirableat least with the now customary coatingmaterials, air pressure and spraying speedsI have found that my herepresented nozzles :can 'be considerably varied in the disposition of theauxiliary ports so as to meet dilferent operating conditions.

Thus in Fig. 3, the port axes a converge at an angle of =60 degrees; sothat each such port axis is almost at right angles to the portion of thedotted curve '7 toward which the .jet from that port is directed. Thusarranged, the portions of the air of each such jet which are adjacent tothe plane 2 in which the spray is to be flattened (and along which thematerial stream is flattened for that purpose) effectivelyresist thespreading of the stream to some extent, while jet portions farther fromthat plane are initially deflected "by the material so that each suchair jet presents a portion a which straddles the impacted shoulderportion of the flattenedmaterial stream, as shown in Fig. 14, beforemerging with the latter. This straddling probably accounts for aconsiderable part of the resulting smoothing of the contour of the spraypattern. 7

When the axes a of the auxiliary ports converge at an angle of 40degrees, as in Fig. '9, the auxiliary jets exert a larger share of theirenergy in the direction in which the material stream "was projected, soas to contribute more toward the velocity of the stream; and the extentof this stream-propelling effect is increased still more when the saidport axes a converge at an angle :of

only degrees, as in Fig. 1'0. Moreover, instead of making the auxiliaryports with cylindrical bores, as in Figs. 3 and 10, these may havetapering bores increasing forwardly in diameter, as shown for the portsa of Fig. 9, so that each projected auxiliary .air jet will have more ofa stream-straddling effect.

Comparing Fig. 10 with Figs. 1 and9, it will be noted that theintersection of the axes a. of the auxiliary jets intersecting at apoint 1 which advances forwardly as the angle of convergence betweenthese jet axes is decreased; so that this intersection point I in Fig. 3is fully 50 percent farther forward from the starting point of theprojected material stream than the intersection X of the-axes of theside airjets.

This increase in the forward spacing of the point I grows as the angleof convergence 8 of the jet axes decreases, as shown successively inFigs.f9 and 10; and in practice this angle can be decreased to :zero, asin Fig. .11., by making the auxiliary jet axes parallel, provided thatthe auxiliary jets are freely spaced from the not yet flattened part ofthe material stream and are sufficiently near that stream part so thatthe axis of each such jet will intersect the impacted shoulder portionof the flattened stream at an inwardly open'acute'angle '6 of at leastabout 45 degrees. With the material stream flattened to the maximumextent now customary for spray guns, this angle 8 canbe'fully 80degrees, as in Fig. 3-, where the jet :axes a converge at an angle of 60degrees; but I have found that any increase of the said angle ii beyondabout 80 degrees would be detrimental for my purpose, because theauxiliary jets then will unduly shorten the spray pattern.

Moreover, within the here illustrated desirable range of the angle ofconvergence 8 between the axes of my auxiliary jets-namely between 60degrees andzero-a "major portion or the energy of each such jet isexpended in accelerating the velocity of the projected material, so aspartially to offset the velocity-retarding due to the irm pact of thestream-flattening side air jets,

Since this acceleration increases as the said angle of convergence isdecreased, while the offspray-preventing and pattern-smoothing effectincreases with an enlargement of the said angle, I can readily adapt mynew air nozzle to widely varying materials by merely varying the angleat which each auxiliary port is bored, with respect to the axis of thecentral air port C. S0 also, I can vary both the velocity-acceleratingor spray-propelling effect and the extent to which my auxiliary air jetscontribute to the atomization of the spray :by varying the borediameters of the auxiliary ports, or by making each such bore flareforwardly somewhat. Thus, Fig. 1 3 shows each auxiliary port A as havinga forwardly flaring bore, which I have found particularly desirablewhenthe spacing of the material nozzle tip T from the bore of the centralair port 0 is unusually small so that additional air is needed foradequately atomizing the material.

However, while I have heretofore described my invention in connectionwith an air nozzle of otherwise conventional type, it should be obviousthat my novel spray-improving method does not hinge on the hereparticularly illustrated means for projecting the needed auxiliary airjets.

So also, whileI have particularly mentioned the advantages which myinvention affords by preventing olf-spray with certain materialssuch asvitreous enamels, glazings and so-called sy thetic enamelsI have alsofound my here described air nozzle desirable with many homogeneousmaterials, such as lacquers, because it permits a higher spraying speedto be obtained without reducing the degree of atomization and .withoutintroducing any streaking of the spray or "tendency to split the spray.

I claim as my invention:

1. In the production of a flattened spray of material by the projectingof forwardly converging jets of air against opposite sides of aprojected stream of material so as to deform the stream of a fan-shapedcontour presenting rearwardl-y facing and laterally opposite contourshoulders near the unflatt'en-ed part of the stream, the method ofpreventing a fraying of the side edges of the said fan-shaped contour,which method consists in forwardly projecting two jets of air freelyspaced from the not yet flattened part of the material stream anddirected respectively against the said shoulders, with the axes of thetwo jets disposedin the plane along which."

the stream is flattened and symmetrical with respect to the axis of theprojected stream, and with the said jet axes converging forwardly at anangle of not more than 60 degrees.

2. The method recited in claim 1, in which each of the said jets isformed of such a, diameter as to cause the jet to straddle the shoulderportion against which that jet is directed, before all of the air of thejet merges with the material of the stream.

3. The method of smoothing contour portions of the pattern produced by aforwardly projected stream of material after the said stream has beenflattened along a plane diametric of the stream by the impact of opposedjets of air having their axes intersecting on the axis of the saidstream, which method comprises the simultaneous projection, againstfan-shoulders of the flattened stream portion, of two opposed auxiliaryjets of air having their axes disposed in the said plane andintersecting on the axis of the stream at a point at least 50 percentfurther forward from the starting point of the stream than the aforesaidintersection; and with the axis of each auxiliary jet engaging afan-shaped edge portion of the flattened stream part at a major acuteangle opening toward the stream portion back of that stream part.

4. A spray appliance of the class in which a forwardly projected streamof aerated material is flattened, by the impact of two forwardlyconverging side jets of air against opposite sides of the stream, to afan shape presenting two rearwardly convexed shoulders at opposite sidesof the axis of the stream, and in which the axes of the said side jetsare a plane diametric of the axis of the projected. stream,characterized by including means for projecting two auxiliary andforwardly converging jets of air with their axes disposed in a secondplane diametric of the stream axis and at right angles to the aforesaidplane; the said auxiliary jets having their axes intersecting at a pointon the stream axis farther forward from the starting point of the streamthan the intersection of the said side jets, the

auxiliary jets being directed respectively against is flattened along aplane housing the axis of the,

stream, by the impact of two forwardly converging side jets againstopposite sides of the stream, to a fan shape presenting two rearwardlyconvexed shoulders at opposite sides of the axis of the said stream, andin which the axes of the said side jets are a plane diametric of theaxis of the projected stream, characterized by including means forforwardly projecting two auxiliary jets of air symmetrically withrespect to the stream axis, with the axes of the auxiliary air jetsdisposed in the said plane and directed respectively against portions ofthe said two shoulders adjacent to the juncture of the said shoulderswith the not yet flattened part of the stream; and with the axis of eachauxiliary jet at an angle of between zero and 30 degrees to the axis ofthe said stream, and at an inwardly open major acute angle to the edgeof the shoulder against which 5 that jet is directed.

'7. A spray appliance as per claim 6, in which the said means areconstructed so that each auxiliary air jet initially flares forwardly ata cone taper angle of between zero and approximately 10 20 degrees.

8. In a spray appliance of the class in which a stream of material isprojected forwardly through an axial port in an air nozzle, and in whichthe air nozzle also has side air ports for projecting 15 side jets ofair forwardly respectively against opposite sides of the said streamalong forwardly converging axes having their intersection on the axis ofthe said central port, whereby the side air jets flatten the materialstream to cause the 20 latter to present rearwardly and laterally bowedshoulders at opposite sides of the axis of the said stream; an airnozzle characterized by having in addition to the said central air portand side air port two auxiliary ports of smaller diam- 25 eter than theside air ports; the said auxiliary ports having their axes in the planealong which the stream is flattened and being disposed for projectingair along axes which intersect on the axis of the material stream at apoint at least one 30 half farther from the outlet of the said centralair port than the aforesaid intersection; the angle at which the axes ofthe auxiliary ports converge being materially less than the angle ofconvergence of the axes of the side air ports, and. 35 the saidauxiliary port axes being disposed so that the air projected by theseports is directed respectively against portions of the said shoulderswhich are near to but spaced from the rear end of the stream part whichis flattened by the side air jets.

9. A spray head comprising means for forwardly projecting an aeratedstream of material, means for projecting two forwardlyv converging sidejets of air against opposite sides of the projected material stream toproduce a flattened stream portion presenting laterally oppositelydirected and rearwardly convexed shoulders near the not yet flattenedportion of the said stream; and means for projecting two forwardlyconverging auxiliary air jets respectively against and in initiallystraddling relation to the said shoulders, with the axes of theauxiliary air jets disposed in the plane along which the said streamportion was flattened, the last named jetaxes intersecting at a point onthe axis of the stream which is at least one-half farther forward fromthe starting point of the projected material stream than theintersection of the said side air jets.

10. For use in a flat spraying appliance, an air 60 nozzle having at itsfront the usual central air port, and the usual forwardly convergingside air ports presenting their axes in a common plane diametric of thecentral air port and having'their said axes intersecting on the axis ofthe said 65 central port; the air nozzle being characterized by alsohaving two auxiliary air ports, symmetrically disposed with respect tothe central air port and with their axes in a second plane diametric ofthe central air port and at right angles 70 to the said plane; the saidauxiliary ports having their axes intersecting on the said central portaxes at a point at least one-half farther forward from the outlet of thecentral air port than the intersection of the axes ofv the sideairports.

11. A spray appliance of the class in which a forwardly projected streamof aerated material is flattened along a plane housing the axis of thestream, by the impact of two forwardly converging side jets againstopposite sides of the stream, to a fan shape presenting two rearwardlyconvexed shoulders at opposite sides of the axis of the said stream, andin which the axes of the said side jets are in a plane diametric of theaxis of the projected stream, characterized by including means forforwardly projecting two auxiliary jets of air symmetrically withrespect to the stream jet axis, with the axes of the auxiliary airdisposed in the first recited plane and directed respectively againstportions of the said two shoulders adjacent to the juncture of the saidshoulders with the not yet flattened part of the stream, with the axisof each auxiliary jet at an angle of between zero and degrees to theaxis of the said stream, and with each auxiliary jet axis at a majoracute angle, opening toward the axis of the material stream, to the edgeof the shoulder portion against which that jet is directed.

12. In a spray appliance of the class in which a forwardly projectedstream of aerated material is flattened, by the impact of two forwardlyconverging side jets against opposite sides of the stream, to a fanshape presenting two rearwardly convexed shoulders at opposite sides ofthe axis of the stream, and in which the axes of the said side jets area plane diametric of the axis of the projected stream, an air nozzleincluding means for projecting two auxiliary jets of air forwardly tocause these air jets to impact directly against and in straddlingrelation to portions of the said shoulders near the juncture of theseshoulders with the not yet flattened part of the said stream, with theauxiliary jets symmetrically disposed with respect to and projected atopposite sides of the material stream; and with the axes of theauxiliary jets disposed in a second plane along the axis of the streamand at right angles to the ERIC GUSTAFSSON.

